24 lines
511 B
OCaml
24 lines
511 B
OCaml
let digit x y z = function
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1 -> [x]
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| 2 -> [x;x]
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| 3 -> [x;x;x]
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| 4 -> [x;y]
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| 5 -> [y]
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| 6 -> [y;x]
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| 7 -> [y;x;x]
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| 8 -> [y;x;x;x]
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| 9 -> [x;z]
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let rec to_roman x =
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if x = 0 then []
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else if x < 0 then
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invalid_arg "Negative roman numeral"
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else if x >= 1000 then
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'M' :: to_roman (x - 1000)
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else if x >= 100 then
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digit 'C' 'D' 'M' (x / 100) @ to_roman (x mod 100)
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else if x >= 10 then
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digit 'X' 'L' 'C' (x / 10) @ to_roman (x mod 10)
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else
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digit 'I' 'V' 'X' x
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